Neuroimmunity

Neuroimmunity refers to the integrated, bidirectional communication between the nervous and immune systems, mediated by shared signaling molecules, reciprocal receptor expression, and direct anatomical connections. Once regarded as autonomous entities, these systems are now recognized as functionally interdependent: immune cells respond to neurotransmitters and neuropeptides, while neurons and glial cells sense and respond to cytokines and other immune-derived mediators. In peripheral tissues, neural innervation of lymphoid organs and mucosal barriers enables rapid modulation of immune activity, while the gut–brain axis integrates microbial, immune, and neural signals. Within the central nervous system, specialized cellular and structural interfaces—including microglia, astrocytes, and the blood–brain barrier—coordinate immune surveillance and inflammatory responses while shaping synaptic plasticity and regulating molecular exchange between blood and brain. Under physiological conditions, neuroimmune signaling maintains homeostasis, supports brain development, and enables adaptive responses to environmental challenges. Dysregulation of these processes—through chronic glial activation, blood–brain barrier dysfunction, and self-amplifying inflammatory circuits—contributes to neurodegenerative disorders, chronic pain syndromes, and psychiatric illnesses. This encyclopedia article provides a mechanistic overview of neuroimmune communication, highlighting how integrated neuroimmune networks support physiological function and how their disruption underlies diverse pathologies.